Olefin polymerization catalyst and polymerization process

ABSTRACT

A method for making polymerization catalysts is disclosed which comprises contacting a soluble complex prepared from the combination of a metal dihalide and a transition metal compound with a particulate material comprising zirconium phosphate and then reacting the resulting mixture with an organoaluminum halide to produce a catalyst precursor. The catalyst precursor is then contacted with a halogen containing compound selected from halides of Groups IVA and VA to produce the catalyst. Novel catalysts prepared in accordance with the invention method, novel polymerization processes therewith and novel polymers having relatively high melt flow rates while retaining good mechanical strength are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of prior application, Ser. No.07/808,782, filed Dec. 16, 1991, now U.S. Pat. No. 5,231,065.

Field of the Invention

This invention relates to a process for forming catalysts which can beused with a cocatalyst to form a catalyst system for the polymerizationof α-olefins. In one aspect, the present invention relates to novelpolymerization catalysts. In another aspect, the present inventionrelates to a process for polymerizing α-olefins. In yet another aspect,this invention relates to novel polymers of α-olefins.

BACKGROUND OF THE INVENTION

The polymerization of α-olefins and mixtures thereof at low pressures isknown to be promoted by coordination catalysts prepared from mixtures ofcompounds of (a) transition elements, and (b) organometallic compoundsof elements of Groups IA to IIIA of the Periodic Table. Suchpolymerizations can be carried out in suspension, in solution, in thegas phase, and the like.

Because of favorable process economics, especially with low molecularweight olefins such as ethylene and propylene, it is frequentlydesirable to carry out olefin polymerization or copolymerizationreactions in an inert diluent at a temperature at which the resultingpolymer or copolymer does not go into solution; and where the polymerproduct is recovered without removing the polymerization catalyst. Thus,elaborate steps to remove catalyst from the polymer product are avoided.In order for this more economical method of polymer manufacture to bepractical, the polymerization catalyst employed must be capable ofproducing polymer in high productivities in order to maintain theresidual catalyst level in the final polymer at a very low level. Thus,the activity of an olefin polymerization catalyst is one importantfactor in the continuous search for catalysts useful for thepolymerization of α-olefins. It is also desirable to produce polymerparticles which are characterized by high crush or attrition resistantstrength, uniformity of size, and a relatively low level of fineparticulate matter. Although polymer fluff having relatively highpercentages of polymer fines can be handled with plant modifications,the production of polymers in high productivity with low level of finescontent is highly desirable so as to avoid the need for such plantmodifications.

For certain applications of the polymer, such as for example injectionmolding, it is desirable that the polymer exhibit easy processibility,characterized by a high melt flow rate. Often the achievement of a highflow rate results in detriment to the mechanical properties of thepolymer, e.g., the strength of molded parts made from the polymer isreduced.

It would therefore be desirable to produce a polymer which has a highmelt flow rate and yet still retains strength during and afterprocessing.

OBJECTS OF THE INVENTION

It is an object of the present invention, therefore, to provide a noveland improved method for preparing catalyst compositions.

Another object of the present invention is to provide a novel catalystcomposition well adapted for the polymerization of α-olefins.

Another object of the present invention is to provide an improvedprocess for the polymerization α-olefins.

Yet another object of this invention is to provide polymer compositionshaving relatively high melt flow rates while retaining strength duringand after processing.

These and other objects of the present invention will become apparentfrom the disclosure, figures, and claims herein provided.

STATEMENT OF THE INVENTION

In accordance with the present invention, we have discovered thatpolymers which exhibit relatively high melt flow rates while retaininggood mechanical properties are obtained when prepared by polymerizationof α-olefins with high activity, high stereospecificity heterogeneousolefin polymerization catalysts prepared by contacting a soluble complex(produced by contacting a metal dihalide with a transition metalcompound) with a particulate material comprising zirconium phosphateprior to contacting with an organoaluminum halide. After treatment withthe organoaluminum halide the resulting catalyst precursor is activatedfor polymerization by treatment with an activating agent comprisingGroup IVA, IVB, or VB halides.

The invention catalyst can be used with various cocatalyst components toform a polymerization system. By varying components of the system andthe amount of hydrogen employed in the polymerization, a variety ofpolymers having different melt flows and molecular weight distributionscan be produced.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 graphically depicts the relationships between polymerization timeand invention catalyst productivity and between the amount of hydrogenemployed in the polymerization and invention catalyst productivity.

FIG. 2 graphically depicts the relationship between the amount ofhydrogen used in the polymerization and the melt flow rate of thepolymer.

FIG. 3 graphically depicts the relationships between heterogeneity index(HI) and weight average molecular weight (Mw) and number averagemolecular weight (Mn) for polymers prepared by the invention catalyst.

FIG. 4 graphically depicts the relationship between polymerizationreaction time and productivity of the invention catalyst at variouslevels of hydrogen in the reactor.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided a method forthe preparation of an olefin polymerization catalyst which comprises:

(a) contacting at least one metal dihalide selected from the groupconsisting of Group IIA and IIB dihalides with at least one transitionmetal compound in the presence of a diluent under conditions suitablefor the formation of a soluble complex;

(b) contacting the soluble complex produced in accordance with step (a)with a particulate material comprising zirconium phosphate to produce afirst mixture;

(c) contacting said first mixture with an organoaluminum halide toproduce a catalyst precursor;

(d) contacting, the catalyst precursor with a Group IVA, IVB, or VBhalide to activate the catalyst. The catalyst can also be furthercontacted with a cocatalyst, if desired.

Further in accordance with the present invention, there are providednovel catalyst compositions produced as described hereinabove.

Still further in accordance with the present invention there is provideda process for the polymerization of α-olefins having 2-20 carbon atomswhich comprises contacting at least one of said α-olefins underpolymerization conditions with catalyst prepared as describedhereinabove.

Still further in accordance with the present invention there is provideda polymerization process using the invention catalyst in which catalystproductivity is optimized by employing an optimum amount of hydrogen.

Still further in accordance with the present invention, there areprovided novel polymer compositions produced through the employment ofthe novel catalyst which exhibit relatively high melt flow rates whileretaining good mechanical properties.

Examples of Group IIA and IIB metal dihalides that can be used informing the first component of the catalyst include, for example, thedihalides of beryllium, magnesium, calcium, and zinc. Dichlorides arepreferred. Magnesium dichloride is presently preferred because it isreadily available and relatively inexpensive and has provided excellentresults. While the hydrous or anhydrous form of the metal dihalide canbe employed as the starting material for the catalyst; the amount ofwater in the metal dihalide should be from about 0.5 to about 1.5moles/mole magnesium dihalide prior to contacting the dihalide with thetransition metal compound. Any method known to those skilled in the artto limit the amount of water in the magnesium dihalide can be employed.It is preferred to admix the appropriate amount of water with theanhydrous metal dihalide to achieve the ratios set out above.

The metal dihalide component is generally used in the form of aparticulate solid to facilitate its reaction with the transition metalcompound. It is also noted that various techniques for converting ametal halide compound to a fine particulate form, such as for exampleroll milling, reprecipitating, etc., can be used to prepare the metalhalide compound for use according to the present invention. Suchadditional preparation of the metal halide compound promotes thereaction of the metal halide compound with the transition metalcompound. It does not appear, however, to be critical that the metaldihalide compound is in a fine particulate form, since catalystproductivity does not seem to be a function of the size of the particlesof the metal halide compound employed.

The transition metal compounds useful in this invention are thosewherein the transition metal is selected from the Groups IVB and VB andthe transition metal is bonded to at least one atom selected from thegroup consisting of oxygen, nitrogen, and sulfur; and said oxygen,nitrogen, and sulfur atoms are in turn bonded to a carbon of acarbon-containing radical.

The transition metal is preferably selected from titanium, zirconium,and vanadium, although other transition metals can be employed.Excellent results have been obtained with titanium compounds and theyare therefore preferred. Some of the titanium compounds suitable for usein the instant invention include but are not limited to, titaniumtetrahydrocarbyloxides, titanium tetraimides, titanium tetraamides andtitanium tetramercaptides. Other transition metal compounds include, forexample, zirconium tetrahydrocarbyloxides, zirconium tetraimides,zirconium tetraamides, zirconium tetramercaptides, vanadium tetraamides,and vanadium tetramercaptides.

The titanium tetrahydrocarbyloxides are preferred because they produceexcellent results and are readily available. Preferred titaniumtetrahydrocarbyloxide compounds include those expressed by the generalformula Ti(OR)₄, wherein each R is individually selected from an alkyl,cycloalkyl, aryl, alkylaryl, and arylalkyl hydrocarbon radicalcontaining from about 1 to about 20 carbon atoms per radical. Titaniumtetrahydrocarbyloxides in which the hydrocarbyl group contains fromabout 1 to about 10 carbon atoms per radical are more frequentlyemployed because they are more readily available. Suitable titaniumtetrahydrocarbyloxides include, for example, titanium tetramethoxide,titanium dimethoxidediethoxide, titanium tetraethoxide, titaniumtetra-n-butoxide, titanium tetrahexyloxide, titanium tetradecyloxide,titanium tetraeicosyloxide, titanium tetracyclohexyloxide, titaniumtetrabenzyloxide, titanium tetra-p-tolyoxide and titaniumtetraphenoxide.

Of the titanium tetrahydrocarbyloxides, titanium tetraalkoxides aregenerally preferred and titanium tetra-n-butoxide is particularlypreferred because of the excellent results obtained employing thismaterial. Titanium tetra-n-butoxide is also generally available at areasonable cost.

The molar ratio of the transition metal compound to the metal dihalidecompounds can be selected over a relatively broad range. Generally themolar ratio is within the range of about 10:1 to about 1:10, however,the preferred range is about 2:1 to about 1:2. When titaniumtetrahydrocarbyloxide and magnesium dichloride are employed, the molarratio of titanium to magnesium of about 1:2 is most preferred.

The metal halide compound and the transition metal compound employed inthe present invention are normally mixed together by heating, e.g.,refluxing, in a suitable dry (essential absence of water) solvent ordiluent, that is essentially inert to these components and the product.The term "inert" is used to mean that the solvent does not chemicallyreact with the dissolved components or the product once formed. Suchinert solvents or diluents include, for example, n-pentane, n-heptane,methylcyclohexane, toluene, xylenes, and the like. Aromatic solvents arepreferred, such as for example xylene, because the solubility of themetal dihalide compound and the transition metal compound are higher inaromatic solvents than in aliphatic solvents, particularly at lowtemperatures. Such mixing temperatures are generally within the range offrom about 0° C. to about 50° C. and preferably from about 10° C. toabout 30° C.

Mixtures of two or more of the above solvents to dissolve the reagentsof the first catalyst component can also be used and can be readilydetermined by one of ordinary skill in the art.

Generally the amount of solvent or diluent employed can be selected overa broad range. Usually the amount of solvent or diluent is within therange of about 20 to about 100 cc per gram of metal dihalide. Thetemperature employed during the heating step can also be selected over abroad range. Normally the heating temperature is within the range ofabout 15° C. to about 150° C. when the heating step is carried out atatmospheric pressure. Higher heating temperatures can be employed if thepressure employed is above atmospheric pressure.

Generally, the time required for heating these two components togetheris within the range of about 5 minutes to about 10 hours, although inmost instances a time within the range of about 15 minutes to about 3hours is sufficient. Following the heating operation, the resultingsolution can be filtered if desired to remove any undissolved materialor extraneous solids.

In one embodiment of the present invention, it has been found that veryuseful catalyst components result if a third component or set ofcomponents is included during the reaction of the metal dihalide and thetransition metal compound. Many combinations of third components andspecific transition metal compounds provide significant improvements ineither productivity or selectivity for the more desirable insolublepolymer product.

Examples of compounds suitable for use as third components includeelectron donors such as ammonia, hydroxylamine, alcohols, ethers,carboxylic acids, esters, acid chlorides, amides, nitriles, amines,phenols, naphthols, and their sulfur-containing analogs, i.e.,thiophenols. The preferred compounds are aromatic compounds selectedfrom the group consisting of phenols, thiophenols, naphthols, aralkylalcohols, aromatic acids, and aromatic esters.

The molar ratio of third component compound employed in step (1)relative to the transition metal compound can vary from about 5:1 toabout 1:5, preferably about 1:1 to 2:1.

The term "phenol" is used herein to refer to substituted as well asunsubstituted phenols. Typical examples include phenol, O-methyl phenol,n-methyl phenol, p-methyl phenol, 4-phenyl phenol, O-fluorophenyl,m-fluorophenol, p-fluorophenol, p-sec-butylphenol, p-ethyl phenol,p-isopropyl phenol, p-tert-butyl phenol, p-methoxy phenol,p-cyanophenol, and p-nitrophenol. The term aromatic ester is usedgenerally to include substituted as well as unsubstituted aromaticesters. Typical examples include ethyl benzoate, ethylp-methoxybenzoate, ethyl toluate, ethyl p-butoxybenzoate, and butylbenzoate. The preferred aromatic esters are those having 8 to 12 carbonatoms per molecule.

When an ester and a phenol are employed, typically the sum of the molesof those two electron donors to the moles of the transition metalcompound are in the range of about 5:1 to 1:5, more preferably 3:1 to2:1.

The dihalides and the transition metal compounds and electron donors,when employed, can be reacted in the presence of a liquid diluent orsolvent; or when at least one of the reagents is in the liquid stateduring the reaction, the use of a diluent can be omitted.

In accordance with the present invention, the soluble complex preparedas described above is then contacted with a particulate materialcomprising zirconium phosphate to form a first mixture of said solublecomplex and said zirconium phosphate. As used herein, the term phosphateincludes orthophosphates, pyrophosphates, metaphosphates, andpolyphosphates. For convenience, hereinafter these phosphates will becollectively represented by the formula "ZrPO₄ ".

The ZrPO₄ can be prepared by any suitable method. Coprecipitation is thepreferred method, for example, the ZrPO₄ can be prepared bycoprecipitating any suitable zirconium salt with any suitable phosphate.The coprecipitation can be carried out in any suitable solvent such aswater or alcohol with water being the preferred solvent. The metal saltsand the phosphate must be soluble in the solvent used to be suitable.

If a phosphate such as diamonium phosphate is utilized, the pH of thesolution will generally be such that precipitation will occur. However,if other phosphates are used, it may be necessary to add a base such asammonia to achieve a pH which will result in the desired precipitation.

The precipitant formed is typically washed, dried, and calcined in thepresence of a free oxygen containing gas such as air to form the ZrPO₄.

The drying of the precipitant may be accomplished at any suitabletemperature. Generally a temperature of about 20° C. to about 200° C.,preferably about 100° C. to about 150° C., is utilized for a time in therange of about 1 hour to about 30 hours.

The calcining step can be utilized to remove traces of nitrates, tracesof carbon, and water and to make the structure of the ZrPO₄ compositionharder. Any suitable calcining temperature can be utilized. Generally,the calcining temperature will be in the range of about 100° C. to about900° C. with a temperature in the range of about 300° C. to about 600°C. being preferred for a time in the range of about 1 to about 24 hours,preferably about 2 to about 6 hours.

The ZrPO₄ can have any suitable surface area and pore volume. Ingeneral, the surface area will be in the range of about 2 to about 400m² /g, preferably about 10 to about 200 m² /g, while the pore volumewill be in the range of about 0.2 to about 4.0 cc/g, preferably about0.4 to about 2.0 cc/g.

Any suitable phosphates may be utilized to prepare the ZrPO₄. Suitablephosphates include (NH₄)H₂ PO₄, (NH₄)₂ HPO₄, (NH₄)₃ PO₄, (NH₄)₄ P₂ O₇,corresponding phosphates and pyrophosphates of lithium, sodium,potassium, rubidium, and cesium, and H₃ PO₄. Phosphonic acids such asphenyl phosphonic acids and the metal salts of phosphonic acids may alsobe used to derive phosphates for the catalyst composition if desired.

Any suitable zirconium to phosphorus ratio may be used. The ratio willgenerally be about stoichiometric.

The ZrPO₄ containing material can optionally include other transitionmetals selected from Groups IVB-VIB, VIII, IB, and IIB of the PeriodicTable, for example Fe, Co, Ni, Cu, and Zn. Preferred metals are Fe, Ni,and Cu; most preferred is Ni. The molar ratio of the metal component toZr in the ZrPO₄ containing particulate material is generally in therange of 0.0:1 to 10:1. When Ni is chosen as the metal component, themolar ratio is preferably 0.25:1 to 5:1.

The additional metal components are preferably added by coprecipitationduring the formation of the ZrPO₄. A suitable metal salt can be addedwith the zirconium salt and suitable phosphate in any order.

It has also been discovered that the activity of the final catalyst canbe increased for propylene polymerization by forming the ZrPO₄ in thepresence of sulfate ions. Any suitable source of sulfate ions can beemployed. It is presently preferred to use ammonium sulfate to providethe sulfate ions.

The amount of sulfate ions employed is generally within the molar ratioof sulfate ions to Zr ions of about 0.1:1 to 10:1.

The quantity of particulate material comprising ZrPO₄ employed in thepractice of the present invention, based on the weight of initial metaldihalide employed, can vary over a wide range. Generally, the weightratio of ZrPO₄ containing particulate material to metal dihalide canrange from about 0.05:1 up to about 25:1, with ratios in the range ofabout 1:1 to 10:1 preferred.

The desired quantity of ZrPO₄ containing material is added to thesoluble complex once preparation of the soluble complex is complete. Thecombination of ZrPO₄ material and soluble complex is then stirred at anysuitable temperature for any suitable period of time. Generally, thecontacting takes place from in the range of about 5 minutes up to 2hours at a temperature in the range of about 20° up to 100° C., beforefurther treatment of the first mixture with an organoaluminum halide asdescribed below.

The organoaluminum halide is selected from compounds having the generalformula AlR_(n) X₃.sbsb.-n wherein each R is individually selected fromsaturated and unsaturated hydrocarbyl radicals containing 1 to 20 carbonatoms per radical, X is a halogen and n is any number such that 1≦n≦2.Typical examples include methylaluminum dibromide, ethylaluminumdichloride, ethylaluminum diiodide, isobutylaluminum dichloride,dodecylaluminum dibromide, dimethylaluminum bromide, diethylaluminumchloride, diisopropylaluminum chloride, methyl-p-propylaluminum bromide,di-n-octylaluminum bromide, diphenylaluminum chloride, triethylaluminum,dicyclohexylaluminum bromide, dieicosylaluminum chloride, methylaluminumsesquibromide, ethylaluminum, sesquichloride, ethylaluminum sequiiodideand mixtures thereof. Ethylaluminum sesquichloride, ethylaluminumdichloride, and diethylaluminum chloride have been employed with goodresults and are preferred. The most preferred organoaluminum halide isethylaluminum sesquichloride.

The reaction with the organoaluminum halide can also be carried outeither in the presence of a liquid diluent or in the absence of suchdiluent, when at least one of the reagents is in the liquid state.Preferably, the first mixture is contacted with a hydrocarbon solutionof the organoaluminum halide.

The temperature employed while mixing the first mixture andorganoaluminum halide as above-described can be selected over a broadrange. Generally the temperature employed is within a range of about 0°C. to about 50° C. or higher, while temperatures within the range of 20°C. to about 30° C. are preferred. Since heat is evolved when the firstmixture and the organoaluminum halide are mixed, the mixing rate isadjusted as required and additional cooling is employed if necessary inorder to maintain a relatively constant mixing temperature. Aftercompleting the mixing, the resulting slurry is stirred or agitated for asufficient time, generally within a range of about 15 minutes to about 5hours to insure that mixing of the components is complete. Thereafter,stirring is discontinued and the solid product catalyst precursor isrecovered by filtration, decantation, and the like. The precursor isthen washed with a suitable material such as a hydrocarbon, e.g.,n-pentane, n-heptane, cyclohexane, benzene, xylenes, and the like, toremove any soluble material which may be present. The catalyst precursoris reactive and if it is to be stored before use, it must be protectedagainst unwanted reactions and contamination.

The molar ratio of the transition metal compound in the first mixture tothe organoaluminum halide can be selected over a relatively broad range.Generally, the molar ratio of the transition metal of the first mixtureto the organoaluminum halide is within a range of 10:1 to 1:10, and morepreferably within a range of about 2:1 to abut 1:3, since a molar ratiowithin the latter range usually produces an especially active olefinpolymerization catalyst.

The catalyst precursor is then reacted with a halogen-containingcompound of Groups IVA, IVB, and VB.

The particularly preferred halogen-containing compounds of Groups IVA,IVB, and VB are chlorine-containing compounds of Ti, Si, Ge, Sn, P, andC. Typical examples include TiCl₄, COCl₂, PCL₃, SiCL₄, SnCl₄, CCL₄, andacid chlorides of the formula R'COCl where R' is an aliphatic oraromatic radical, preferably containing 1 to 20 carbon atoms.

Other suitable halogen-containing compounds include chlorosiloxanes ofthe formula Si_(n) O_(n-1) Cl₂.sbsb.n+₂ wherein n is a number in therange of 2 to 7, for example Si₂ OCl₆ ; chlorinated polysilanes havingthe formula Si_(n) Cl₂.sbsb.n+₂ where n is a number in the range of 2 to6, such as Si₄ Cl₁₀ ; chlorinated silanes having the formulaSiH₄.sbsb.-n Cl_(n) wherein n is a number in the range of 1 to 3, suchas SiHCl₃ ; silanes having the formula R'_(n) SiH_(x) Cl_(y) wherein R'is an aromatic or aliphatic radical containing 1 to 20 carbon atoms, x anumber in the range of 0 to 2, and y is a number in the range of 1 to 3,such as C₂ H₅ SiCl₃, CH₃ SiCl₂ H, and (CH₃)₂ SiCl₂ ;alkoxy-halogensilanes of the formula Si(OR)₄.sbsb.-n Cl_(n) wherein R isan alkyl or aryl radical having 1 to 20 carbon atoms and n is a numberin the range of 1 to 3, such as Si(OC₂ H₅)Cl₃.

In a particularly preferred embodiment, a chlorine-containing siliconcompound or an organosilane is employed in combination with TiCl₄.Examples of the preferred silicon compounds for this embodiment includeSiCl₄, HSiCl₃, φSiHCl₂, and φ₂ SiCl₂, wherein φ is a phenyl radical. Inthis embodiment, the ratio of silicon compound to TiCl₄ can varyconsiderably; however, best results are generally obtained if the molarratio of silicon compound to TiCl₄ is about 1:1.

Generally the reaction of the catalyst precursor with thehalogen-containing compound can be carried out neat or in a liquidmedium in which the halogen-containing source is soluble. Accordingly,the catalyst precursor is generally contacted with an inert liquiddiluent containing the halogen-containing source. Any suitable inertdiluent can be employed. Examples of diluents include normally liquidhydrocarbons such as n-pentane, n-heptane, cyclohexane, benzene, andxylene.

The temperature employed in this step can be selected over a relativelybroad range, generally in the range of -25° C. to +250° C., preferably0° C. to 200° C., with a temperature of about 100° C. being mostpreferred.

The treating time can also be selected over a broad range and generallyis within the range of about 10 minutes to about 10 hours. While theweight ratio of the halogen-containing source to the catalyst precursorcan be selected over a relatively broad range, the weight ratio of thehalogen-containing source to the catalyst precursor is generally withina range of about 10:1 to about 1:10, more preferably from about 7:1 toabout 1:4. Following the treatment of the catalyst precursor with thehalogen-containing source, the surplus halogen-containing source isremoved by washing the final solid catalyst with a dry (essentialabsence of water) liquid such as a hydrocarbon of the type previouslydiscussed, n-hexane, or xylene for example. The resulting catalyst canbe stored in the diluent or after drying, stored under dry nitrogen.

An organometallic cocatalyst or mixture of cocatalysts can be employedwith the catalyst of the present invention if desired. Theorganometallic cocatalysts suitable for use in accordance with theinvention can be selected from among the hydrides and organometalliccompounds of metals of Groups IA, IIA, and IIIA of the Periodic Table.Of the organometallic cocatalysts, organoaluminum compounds arepreferred, with the most preferred organoaluminum cocatalysts beingcompounds of the formula R₃ Al and R_(n) AlX₃.spsp.-n which include, forexample, trimethylaluminum, triethylaluminum, triisopropylaluminum,tridecylaluminum, triecosylaluminum, tricyclohexyaluminum,triphenylaluminum, 2-methylpentyldiethylaluminum, andtriisoprenylaluminum, ethyl aluminum dichloride, ethylaluminumsesquichloride, and diethylaluminum chloride.

The molar ratio of the organometallic compounds of the cocatalyst to thetransition metal compound of the catalyst is not particularly criticaland can be selected over a relatively broad range. Generally, the molarratio of the organometallic compounds of the cocatalyst to thetransition metal compound of the catalyst is within a range of about 1:1to about 1500:1. For catalyst systems wherein the cocatalyst comprisesat least one organoaluminum compound, typically about 0.25 to 15milligrams of the titanium-containing catalyst are employed permillimole of organoaluminum cocatalyst.

If desired, at least one Lewis Base can also be employed with theorganoaluminum cocatalyst. Among Lewis bases capable of appropriateaddition are amines, amides, ethers, esters, ketones, arsines,phosphoramides, thioethers, aldehydes, alcoholates, amides, and salts ororganic acids of metals of the first four groups of the Periodic Table.The best results, as regards both activity and stereospecificity, havebeen obtained using an aromatic ester or an amine. Typical examples ofsuitable aromatic esters include ethyl benzoate, ethyl p-methoxybenzoate(ethyl anisate), ethyl o-chlorobenzoate, ethyl naphthenate, ethyltoluate, and ethyl p-butoxybenzoate. Typical examples of suitable aminesinclude ethyl pivalate, 2,2,6,6-tetramethylpiperidine,1,2,4-trimethylpiperazine, and 2,5-dimethylpiperazine. The preferredLewis base: organoaluminum molar ratio is lower than 0.8:1; when anaromatic ester or amine is used, it is generally from 0.1:1 to 0.6:1.

In one embodiment of the present invention a cocatalyst comprisingtriethylaluminum and ethyl anisate has been employed and has been foundto give excellent results. The amount of ethyl anisate can range fromabout 0.1 to about 0.6 moles per mole of triethylaluminuim present.

A variety of polymerizable compounds are suitable for use in the processof the present invention. Olefins which can be homopolymerized orcopolymerized with the invention catalysts include aliphaticmono-1-olefins. While the invention would appear to be suitable for usewith any aliphatic mono-1-olefin, those olefins having 2 to 20 carbonatoms are most often used. Aliphatic mono-1-olefins can be copolymerizedwith other 1-olefins and/or with other smaller amounts of othermonoolefins, alpha-methylstyrene, and similar monoolefins which do notimpair the catalyst.

The catalysts of the invention are well suited for producingstereoregular polypropylene, offering potential for high rates ofpolymer production as well as low formation of soluble polymer.

Polymerization may be conducted in a liquid phase, in liquid monomer inthe presence or absence of an inert hydrocarbon diluent, or in a gasphase. In the polymerization of propylene, particularly satisfactoryresults have been attained operating in the presence of an aliphatic oraromatic hydrocarbon diluent, liquid under the polymerizationconditions, such as propylene, toluene, gasoline, and the like.

The polymerization process according to the present invention employingthe catalysts and cocatalysts as above described can be performed eitherbatchwise or continuously. In a batch process, for example, a stirredautoclave is prepared by first purging with nitrogen and then with asuitable compound, such as isobutane for example. When the catalyst andcocatalyst are employed either can be charged to the reactor first orthey can be charged simultaneously through an entry port under anisobutane purge. After closing the entry port, hydrogen, if used, isadded, and then a diluent such as isobutane is added to the reactor. Thereactor is heated to the desired reaction temperature, which forpolymerizing ethylene, for example, is for best results generally withina range of about 50° C. to about 102° C. and the monomer is thenadmitted and maintained at a partial pressure within a range of about 70to about 725 psig for best results. At the end of the designatedreaction period, the polymerization reaction is terminated and theunreacted olefin and isobutane are vented. The reactor is opened and thepolymer, such as polyethylene, is collected as a free-flowing whitesolid and is dried to obtain the product.

In a continuous process, for example, a suitable reactor such as a loopreactor is continuously charged with suitable quantities of solvent ordiluent, catalyst, cocatalyst, polymerizable compounds and hydrogen, ifany, and in any desirable order. The reactor product is continuouslywithdrawn and the polymer recovered as appropriate, generally byflashing the diluent or solvent and unreacted monomers and drying theresulting polymer.

For optimum productivity of polymer of low solubility in the continuouspolymerization of propylene, it is preferable to contact the cocatalystcomprising the organoaluminum-Lewis Base with the titanium-containingcatalyst for a short period immediately prior to its being exposed toliquid propylene. It is preferable under these circumstances that themolar ratio of organoaluminum to Lewis Base in the cocatalyst be greaterthan 2:1.

Molecular weight of the polymer can be controlled to an extent byvarying the amount of hydrogen present in the reactor duringpolymerization. A greater amount of hydrogen in the reactor generallyproduces lower molecular weight polymer. The flow properties of thepolymer are in turn related to the weight average molecular weight ofthe polymer (Mw). Higher melt flow rates are generally associated withpolymers having broad molecular weight distributions. In addition, lowmolecular weight polymer is usually associated with low mechanicalstrength.

Thus, polymers with broad molecular weight distributions which can havesignificant portions of the polymer which are of relatively lowmolecular weight often suffer from poor mechanical strength.

The invention catalyst, however, has surprisingly been found to producepolymer having high melt flow rates while having narrow molecular weightdistributions. The invention catalyst also exhibits greatly increasedproductivity for a long period when it is employed with certain levelsof hydrogen.

The amount of hydrogen generally employed in the polymerization is inthe range of 0.5-200 psi.

The olefin polymers made with the catalyst of this invention are usefulin preparing articles by conventional polyolefin processing techniquessuch as injection molding, rotational molding, extrusion of film, andthe like.

A further understanding of the present invention and its advantages willbe provided by the following examples illustrating a few embodiments ofthe invention.

EXAMPLE I Procedure I Preparation of Zirconium Phosphate Gel

A solution consisting of 100 ml isopropanol and 13.0 ml orthophosphoricacid (commercially available concentrated reagent) was added to a secondsolution consisting of 300 ml isopropanol and 57.6 g zirconiumtetrabutoxide butanolate. The product gel was filtered, dried, andscreened to various sized fractions. The dried zirconium phosphate gelwas activated by calcining at 300° C. in air for 90 minutes. Subsequentto being calcined the zirconium phosphate gel was flushed with nitrogen.

Procedure II Preparation of Catalyst Precursor

The following is the method used for the preparation of the variousinvention and comparison polymerization catalyst precursors:

A mixture of 0.7 ml H₂ O in 300 ml xylene was added to 3.8 g anhydrousmagnesium chloride in a 9 quart beverage bottle reaction vessel under anargon atmosphere and stirred at room temperature for approximately 16hours. At the completion of this mixing, 6.8 ml of titaniumtetrabutoxide and 1.88 g phenol were added, followed by heating themixture to 100° C. While still hot, 20 grams of a ZrPO₄ or other solidmaterial were added to the reaction mixture followed by stirring for 10minutes. At the completion of stirring, 25 ml of a 25% ethylaluminumsesquichloride solution in heptane was added to the preparationresulting in a solid catalyst precursor. The solid precursor wasisolated by centrifugation and washed several times by slurrying inn-hexane followed by centrifugation until the supernatant liquid wascolorless. The washed material was then isolated by vacuum filtrationand the cake allowed to dry in the glove box overnight.

Procedure III Halogen Exchange (Activation) of the Catalyst Precursor

5 g samples of the solid catalyst precursor produced by application ofprocedures I and II were treated with a solution containing 50 mltitanium tetrachloride, 40 ml trichlorosilane, and 10 ml silicontetrachloride and heated to 100° C. for 1 hour. The resulting solidswere isolated as in procedure II, and stored in a stoppered container ina dry, inert atmosphere until ready for testing.

Polypropylene Polymerization

Propylene polymerization were conducted in a 1 L stirred stainless steelreactor in liquid propylene for the specified residence times at 70° C.in the presence of the specified amount of hydrogen with a weighedportion of the catalyst. Catalyst weights ranged from about 25 to about100 mg. In each run, unless otherwise specified, a cocatalyst consistingof 2.0 mmoles of triethylaluminum (TEA) and 1.1 mmoles of ethyl anisate(EA), premixed, and 2.0 mmoles of diethylaluminum chloride (DEAC) wereemployed. The organometal solutions were each about 0.6 molar inn-heptane.

Following polymerization, the polypropylene was recovered, stabilizedand dried.

Ethylene Polymerization

Ethylene polymerization was conducted in a 2 L stirred, stainless steelreactor containing 1.25 lbs. (567 g) of isobutane diluent at thespecified temperatures, times and in the presence of hydrogen, if used,to control polymer melt index. In each run unless otherwise specified, 1mL of TEA (1 mmole TEA) as a solution in n-heptane, was used ascocatalyst. Total reactor pressure in each run was about 565 psia (3.89MPa). Polymerization was terminated by discontinuing heating, ventinggaseous reactants and recovering and drying the polyethylene produced.

EXAMPLE I

An invention catalyst was prepared as described above by employing thezinconium phosphate gel prepared in Procedure I as the solid material inProcedure II.

Samples of the invention catalyst were tested in propylenepolymerizations using different reaction residence times. Table I setsout the different results obtained in the polymers produced whenemploying residence times ranging from 10 minutes to 4 hours. Thepolymerizations were performed in the presence of 15 psi hydrogen. Thecocatalyst system used was that described above for propylenepolymerization, i.e., 2 moles TEA, 1 mole EA and 2 moles DEAC.

                  TABLE I                                                         ______________________________________                                        Residual     Polymer Characteristics                                          Run No.                                                                              Time (min.)                                                                             Prod. (kg/g)                                                                             MF   Mw    Mn   HI                                ______________________________________                                        1      10        3.1        10   333   41.3 8.1                               2      30        3.6        29   207   33.8 6.1                               3      60        5.8        41   197   37.3 5.3                               4      90        7.1        45   159   30.5 5.2                               5      180       12.8       84   125   29.0 4.3                               6      240       17.0       78   148   25.1 5.3                               ______________________________________                                    

As can be seen from the results set out in Table I, the inventioncatalyst increases in productivity with the longer residence times whilethe heterogeneity index (HI) of the polymer produced using the inventioncatalyst decreases.

EXAMPLE II

A second similar series of polymerizations were performed usingdifferent reactor residence times ranging from 5 minutes to 3 hours. Nohydrogen was present during these runs. The results are shown in TableII.

                  TABLE II                                                        ______________________________________                                        Residual     Catalyst   Polymer Characteristics                               Run No.                                                                              Time (min.)                                                                             Prod. (kg/g)                                                                             MF   Mw   Mn    HI                                ______________________________________                                        7       5        0.82       0.3  919    75.7                                                                              12.1                              8      30        1.1        0.25 920  120   7.7                               9      60        3.7        0.5  817   99   8.3                               10     180       3.4        0.5  836  120   6.9                               ______________________________________                                    

The results in Table II show similar trends with the use of theinvention catalyst as were shown in Table I. Catalyst productivityappears to increase with longer residence times and the HI generallytends to decrease.

EXAMPLE III

Several series of propylene polymerizations were also conducted todetermine the response of the invention catalyst to the amount ofhydrogen present during the polymerization. One series was conductedusing 30 minute residence times and varying the amount of hydrogen fromnone to 200 psi. Three other series were conducted using 1 hour, 2 hour,and 4 hour residence times, again varying the amount of hydrogen fromnone to 200 psig. The results are graphically depicted in FIG. 1. As canbe seen from FIG. 1, the invention catalyst exhibited large increases inproductivity when hydrogen amounts in the range of about 10 to about 50psi were present. It is also noted that the polymerizations using longerresidence times exhibited greater increases in productivity when thelower amounts of hydrogen were present than the shorter polymerizations.The 1, 2 and 4 hour polymerizations also exhibited increasingproductivity when large amounts of hydrogen were used in conjunctionwith the invention polymerization catalyst.

The relationships resulting from use of the invention catalyst betweenMw and HI, and Mn and HI are graphically depicted in FIG. 2. The dataused to prepare FIG. 2 were collected during propylene polymerizationsas described above, using invention catalysts prepared as describedabove with varied amounts of hydrogen and 1/2 hour reactor residencetimes. It appears that HI decreases with decreasing Mw linearly. It alsoappears that HI decreases linearly with decreasing Mn, however, Mwappears to have the greater effect on HI.

EXAMPLE IV

A set of propylene polymerizations was conducted using the inventioncatalyst and a cocatalyst system of 2 moles TEA, 1 mole2,2,6,6,-tetramethylpiperidine (TMP) and 2 moles DEAC. Reactor residencetimes were 30 minutes for all runs and the amount of hydrogen employedwas varied from none to 200 psig. Results are shown below in Table III.

                  TABLE III                                                       ______________________________________                                               Amt.     Polymer Characteristics                                       Run No.  H.sub.2 (psig)                                                                           Mw      Mn     HI   MF                                    ______________________________________                                        11        0         87.1.sup.a)                                                                           25.6   23.4 .sup.  --.sup.b)                      12        5         928     77.9   11.9 14                                    13        10        186     30.9   6.0  26                                    14        20        143     29.6   4.8  35                                    15        50        76.1    19.0   4.0  238                                   16       100        60.1    16.8   3.6    +.sup.c)                            17       150        35.3    12.4   2.9  +                                     18       200        45.1    12.5   3.6  +                                     ______________________________________                                         .sup.a) Column plugged during GPC molecular weight measurements.              .sup.b) Not measured.                                                         .sup.c) Too high to measure.                                             

The results from the above-described runs were compared with the resultsgiven in 1/2 hour polymerizations performed using the invention catalystwith a cocatalyst system of 2 mmoles TEA, 1.1 mmoles EA and 2 mmolesDEAC. The results are depicted in FIG. 3. The relationship between Mwand the amount of hydrogen in the reactor is plotted for the two sets ofpolymerizations. The cocatalyst system which employs TMP appears to havebeen more responsive to hydrogen since Mw increases more rapidly atlower hydrogen concentrations than in the polymerizations using EA inthe cocatalyst.

FIG. 3 also depicts the relationship between MF and the amount ofhydrogen in the reactor for the two sets of polymerizations. It is notedthat the two different cocatalyst systems result in essentially the samecurve.

The effect of reactor residence time on catalyst productivity was alsoinvestigated. Propylene polymerizations were conducted, using theTEA/TMP/DEAC cocatalyst system, for different amounts of time, rangingfrom 5 minutes to 4 hours. The amount of hydrogen used was also variedto see the effects of both time and hydrogen content on catalystproductivity. The results are graphically depicted in FIG. 4. It can beseen that when no hydrogen is present, the catalyst maintains a constantproductivity for residence times of about 1 hour and greater. A similarbehavior is observed when the amount of hydrogen is from about 100-200psi for 2 hours and greater. However, for lower amounts of hydrogen(e.g., 15 and 25 psi), the productivity continues to rise with longerreactor residence times.

EXAMPLE V

This example demonstrates the preparation of an invention catalyst madein the presence of a ZrPO₄ containing nickel.

A Ni-Zr phosphate gel, calculated atom ratios of Ni/Zr of 1:1 andP/Ni+Zr of 1:1, was prepared by adding a hot aqueous solution containing1.2 moles of (NH₄)₂ HPO₄ to hot aqueous solution containing 0.6 moleeach of Ni(NO₃)₂.6H₂ O and ZrOCl₂. 4H₂ O. The gel was filtered, the cakewas washed with several portions of water and the product was dried inan oven for 12 hours at 100° C. Individual portions of the dried gelwere then calcined for 6 hours in a muffle furnace in air at thetemperature indicated below, then ground to less than 20 mesh in size.

19S: 250° C.

20S: 350° C.

21S: 450° C.

22S: 550° C.

A series of catalysts were produced in the presence of a calcined,particulate materials as follows: under argon in separate 1 quart (0.9L) beverage bottles was charged 0.04 mole of particulate MgCl₂.0.008 H₂O, 0.04 mole of H₂ O and 300 mL of reagent quality mixed xylenes. Eachmixture was stirred for about 3 days at 23° C., then to each bottle wasadded 0.02 mole of titanium tetra-n-butoxide (Ti(OBu)₄) and 0.02 mole ofphenol. With continued stirring, each mixture was heated at 100° C. for1 hour to obtain a solution and to each solution was added 20 g of thedesired Ni.ZrPO₄ material. Each mixture was stirred 10-15 minutes as itwas allowed to cool to about 23° C. Then it was treated dropwise with 25mL (0.01 mole) of ethylaluminum sesquichloride (EASC) as a 25 weightpercent solution in n-heptane to produce a composition which settledquickly when stirring ceased. For convenience, these compositions aredesignated catalyst precursors A. Each precursor was isolated bycentrifugation, washed with n-hexane to remove unreacted and/or solubleby-products and dried by standing overnight in the dry, argon-filledglove box. A 5 g portion of each precursor A was activated forpolymerization by treatment for 1 hour at 100° C. with about 30 mL of a3-component halide mixture consisting of 50 volume percent TiCl₄, 40volume percent HSiCl₃ and 10 volume percent SiCl₄. The correspondingweight ratio of mixed halides to initial MgCl₂ used in preparingprecursor A was about 10:1. The resulting compositions were isolated bysuction filtration, washed with n-hexane and dried as before to obtainthe reddish-brown catalysts as particulate solids.

The weights and calcining temperature employed in producing eachsupport, the weights of precursor A and catalyst made therefrom aregiven in Table IVA.

                  TABLE IVA                                                       ______________________________________                                        Supported Catalyst Precursors and Isolated Catalysts Thereof                  Ni--Zr PO.sub.4 gel                                                                                   Atom           Isolated                               Catalyst      Calcining Ratio Precursor A                                                                            Catalyst.sup.(a)                       No.    No.    Temp. °C.                                                                        Ni/Zr Wt. g    Wt. g                                  ______________________________________                                        19     19S    250       1:1   25.1     4.8                                    20     20S    350       1:1   25.8     4.9                                    21     21S    450       1:1   26.2     5.0                                    22     22S    550       1:1   25.1     4.9                                    ______________________________________                                         .sup.(a) From 5 g portion of corresponding precursor A.                  

A weighed portion of each catalyst in Table IVA was employed inpropylene polymerization for 1 hour at 70° C. in a 1 L stirred,stainless steel reactor in liquid propylene. Each run was conducted inthe presence of 25 psi hydrogen and a cocatalyst consisting of 2.0mmoles of triethylaluminum (TEA) premixed with 1.1 mmoles of ethylanisate (EA) and 2.0 mmoles of diethylaluminum chloride (DEAC). Theorganometal solutions were each about 0.6 molar in n-heptane.

Following polymerization, the polypropylene in the reactor wasrecovered, stabilized with conventional antioxidants and dried.Propylene solubles, xylene solubles, calculated productivity, melt flowand flexural modulus were determined as set forth in earlier relatedinventions. The results obtained are given in Table IVB.

                  TABLE IVB                                                       ______________________________________                                        Propylene Polymerization                                                      Weight, mg                                                                                 Calculated            Melt   Flex.                               Cat. Cata-   Prod/.    Wt. % Solubles                                                                            Flow   Mod.                                No.  lyst    kg/g/hr.sup.(a)                                                                         Propylene                                                                             Xylene                                                                              g/10 min.                                                                            MPa                               ______________________________________                                        19   36.3    1.64      2.1     3.5   17.2   1520                              20   36.7    2.61      1.3     3.4   8.0    1600                              21   49.1    3.28      0.9     4.1   4.3    1502                              22   29.7    2.20      3.4     12.1  16.7   1001                              ______________________________________                                         .sup.(a) Based on polymer recovered from reactor excluding                    propylenesoluble polymer.                                                

The results in Table IVB show the invention catalysts based oncalculated productivity values for the whole catalyst to be quite activein propylene polymerization. The optimum calcining temperature for theNi-Zr phosphate material having an atom ratio of Ni/Zr of 1:1 falls inthe 350°-450° C. range. Below this temperature range a moderate declinein catalyst activity results while little effect on polymer solubles isnoted. Above the temperature range a small decline in catalyst activityis observed but a substantial increase in soluble polymer, particularlyxylene-soluble polymer is noted. This effect is reflected in the drop inthe flexural modulus from the 1500-1600 MPa values obtained with thepolymer produced with catalysts 1-3 to about 1000 MPa for the polymermade with catalyst 20. The results suggest that the relatively largeamount of xylene-soluble polymer made with catalyst 20 may be amorphousor less crystalline than the remaining polymer resulting in theprecipitous drop in flexural modulus shown.

EXAMPLE VI

A series of Ni-Zr phosphate gels having a constant atom ratio of P/Ni+Zrbut a variable Ni/Zr atom ratio was prepared in a similar manner to theNi-ZrPO₄ material of Example V. In this series, an aqueous solutioncontaining 0.2 mole of Ni(NO₃)₂.6H₂ O was mixed with an aqueous solutioncontaining sufficient ZrOCl₂.4H₂ O to provide the desired Ni/Zr atomratio. The quantity of Zr salt in the solutions ranged from 0.02 to 0.50mole. Each mixture was then admixed with an aqueous solution containing(NH₄)₂ HPO₄ equal in mole fraction, e.g., 0.25 mole, to the molefraction sum of the Ni and Zr salts, e.g., 0.25 mole. Each resulting gelwas isolated, washed once with 600 mL of water, dried as before andcalcined for 4 hours in air at 450° C. The Ni/Zr atom ratios of thematerials are tabulated below.

    ______________________________________                                                                    Surface                                                             Pore Vol. Area                                                                cc/g      m.sup.2 /g                                        ______________________________________                                        Solid 23S, Ni/Zr atom ratio of 4:1                                                                0.11        38                                            Solid 24S, Ni/Zr atom ratio of 2:1                                                                0.32        86                                            Solid 25S, Ni/Zr atom ratio of 1.3:1                                                              not determined                                            Solid 26S, Ni/Zr atom ratio of 0.8:1                                                              not determined                                            Solid 27S, Ni/Zr atom ratio of 0.7:1                                                              0.31        108                                           Solid 28S, Ni/Zr atom ratio of 0.5:1                                                              0.36        79                                            Solid 29S, Ni/Zr atom ratio of 0.4:1                                                              not determined                                            ______________________________________                                    

All pore volumes and surface areas in this and other examples weredetermined by mercury porosimitry in accordance with the proceduredescribed by American Instrument Company, Silver Springs, Mo., catalognumber 5-7125-B.

All calcined solids in Examples VI, VII, and VIII were ground to lessthan 20 mesh in size.

Catalyst precursors and catalysts therefrom were prepared in thepresence of 20 g of each solid in the manner described in Example V.

The Ni/Zr atom ratio of each solid, the weights of precursor A andcatalysts thereof and the calculated weight percent fraction of eachcatalyst are presented in Table VA.

                  TABLE VA                                                        ______________________________________                                        Catalyst Precursors and Catalysts                                                    Solid                                                                                  Atom               Isolated                                   Catalyst        Ratio     Precursor A                                                                            Catalyst.sup.(a)                           No.      No.    Ni/Zr     Wt. g    Wt. g                                      ______________________________________                                        23       23S      4:1     23.2     4.97                                       24       24S      2:1     23.7     5.12                                       25       25S    1.3:1     21.8     4.90                                       26       26S    0.8:1     21.3     5.00                                       27       27S    0.7:1     21.9     4.95                                       28       28S    0.5:1     22.0     4.40                                       29       29S    0.4:1     23.2     4.80                                       ______________________________________                                         .sup.(a) From 5 g portion of corresponding precursor A.                  

A weighed portion of each catalyst was employed in propylenepolymerization as described in Example V. The results obtained are givenin Table VB.

                  TABLE B                                                         ______________________________________                                        Propylene Polymerization                                                                                          Melt                                           Weight,  Calculated            Flow  Flex.                               Cat. mg       Prod.,    Wt. % Solubles                                                                            g/10  Mod.                                No.  Cat.     kg/g/hr.sup.(a)                                                                         Propylene                                                                             Xylene                                                                              min.  MPa                               ______________________________________                                        23   118.8    1.46      0.6     3.6   33    1611                              24   146.7    0.652     3.0     4.2   10    1459                              25   165.5    0.377     1.5     10.3  31     858                              26   133.1    0.276     4.9     5.0   33    1415                              27   149.0    1.01      1.0     10.8  24    1142                              28   126.1    0.468     4.9     6.2   23    1433                              29    94.2    1.11      1.6     4.1   27    1632                              ______________________________________                                         .sup.(a) Based on polymer recovered from reactor excluding                    propylenesoluble polymer.                                                

The varied productivity results report in Table VB indicate the activepropylene polymerization catalysts are made in the presence of cogelledNi-Zr phosphate xerogels wherein the atom ratio of Ni to Zr can varyfrom at least 4:1 to 0.4:1. The generally high melt flows, generally inthe 20-30 range, suggest that the catalysts are quite responsive to thepresence of hydrogen in the reactor as a molecular weight modifier.Catalysts 25 and 27 made more than 10 weight percent xylene-solublepolymer whereas those catalysts on either side and catalyst 26 in themiddle made much less xylene-soluble polymer. The presence of thesoluble polymer also contributed to the relatively low flexural modulusvalues of 858 and 1142 MPa, respectively, exhibited by the moldedpolymer specimens. The reason for the anomalous behavior is not known.

EXAMPLE VII

A series of catalysts was prepared in the manner described in Example Vemploying, however, 20 g each of solid materials selected fromFe/Co/Zr/PO₄, Ni/Co/Zr/PO₄ and V/Co/Zr/PO₄. The solids were prepared asbefore by precipitating the transition metal-containing phosphate gelsfrom an aqueous solution containing the dissolved transition metal saltswith an aqueous solution of (NH₄)₂ HPO₄. The gels were washed withwater, dried, and calcined in air.

Solid 30S was prepared from 0.108 mole of FeSO₄.7H₂ O, 0.124 mole ofCo(NO₃)₂.6H₂ O and 0.348 mole of ZrOCl₂.4H₂ O with 0.758 mole of (NH₄)₂HPO₄. The calculated atom ratio of Fe+Co to Zr was about 0.7:1 and thecalculated atom ratio of P to Fe+Co+Zr was about 1.3:1. The gel wascalcined for 4 hours in air at 500° C. Pore volume=0.28 cc/g, surfacearea=120 m² /g. Solid 31S was prepared from 0.114 mole of Ni(NO₃)₂.6H₂O, 0.127 mole of Co(NO₃)₂.6H₂ O and 0.354 mole of ZrOCl₂.4H₂ O with0.802 mole of (NH₄)₂ HPO₄. The calculated atom ratio of Ni+Co to Zr wasabout 0.7:1 and the calculated atom ratio of P to Ni+Co+Zr was about1.3:1. The gel was calcined for 4 hours in air at 500° C. Pore volumewas 0.18 cc/g and surface area was 49.6 m² /g.

A V/Co/Zr/PO₄ gel was prepared from 0.190 mole of VOSO₄.5H₂ O, 0.247mole of Co(NO₃)₂.6H₂ O and 0.695 mole of ZrOCl₂.4H₂ O with 1.51 moles of(NH₄)₂ HPO₄. The calculated atom ratios were V+Co/Zr of about 0.6:1 andP to V+Co+Zr of about 1.3:1. The gel was dried and divided into 4portions. Each portion was calcined for 4 hours in air as follows: solid32S°-350° C., solid 33S°-400° C., solid 34S°-450° C. and solid 35S°-500°C.

The transition metals used, weights of precursor A and catalysts thereofare set forth in Table VI.

The pore volume of 35S was 0.87 cc/g and the surface area was 64 m² /g.It is believed that 32S, 33S, and 34S are similar in pore volume andsurface area to those measured for 35S.

                  TABLE VIA                                                       ______________________________________                                        Catalyst Precursors and Catalysts                                             Cata- ZrPO.sub.4 -Containing Solid                                                                     Precursor Isolated                                   lyst                   Calcining                                                                             A       Catalyst.sup.(a)                       No.   No.    Type      Temp. °C.                                                                      Wt. g   Wt. g                                  ______________________________________                                        30    30S    Fe/Co/Zr  500     23.9    3.8                                    31    31S    Ni/Co/Zr  500     20.1    4.6                                    32    32S    V/Co/Zr   350     25.7    4.8                                    33    33S    V/CoZr    400     25.7    4.5                                    34    34S    V/Co/Zr   450     25.3    4.9                                    35    35S    V/Co/Zr   500     25.0    4.9                                    ______________________________________                                         .sup.(a) From 5 g portion of corresponding precursor A.                  

A weighed portion of each catalyst was employed in propylenepolymerization as described in Example V. The results obtained arepresented in Table VIB.

                  TABLE VIB                                                       ______________________________________                                        Propylene Polymerization                                                                                          Melt                                           Weight,  Calculated            Flow  Flex.                               Cat. mg       Prod.,    Wt. % Solubles                                                                            g/10  Mod.                                No.  Cat.     kg/g/hr.sup.(a)                                                                         Propylene                                                                             Xylene                                                                              min.  MPa                               ______________________________________                                        30   124.1    0.362     3.2     2.6   66    1608                              31    91.9    1.92      1.8     7.2   34    1242                              32   125.8    1.04      2.1     8.0   60    1310                              33   135.6    0.444     5.8     6.9    103  1466                              34    90.3    1.23      2.5     4.7   49    1476                              35   133.0    0.255     4.8     4.3   --.sup.(b)                                                                          --                                ______________________________________                                         .sup.(a) Based on polymer recovered from reactor excluding                    propylenesoluble polymer.                                                     .sup.(b) A dash signifies not determined.                                

The productivity results given in Table VIB indicate that activecatalysts can be made in the presence of the various transitionmetal-containing phosphate xerogels. Except for catalyst 33 supported ona Ni/Co/Zr/PO₄ xerogel, the remaining catalysts appear to be even moreresponsive to hydrogen in the reactor, in view of the melt flow valuesof about 50 or higher, than the catalysts of Example VI whereinNi/Zr/PO₄ materials were used in the catalyst preparation.

EXAMPLE VIII

A series of catalysts was prepared in the manner described in Example VIemploying, however, 20 g each of a Cu/Zr/PO₄ gel. The gels wereprepared, washed, dried, and calcined in air in the manner previouslyoutlined in Example VII.

Gel A was prepared from 0.200 mole of Cu(N)₃)₂.2 1/2H₂ O, 0.300 mole ofZrOCl₂.4H₂ O and 0.500 mole of (NH₄)₂ HPO₄. The calculated atom ratio ofCu to Zr was about 0.7:1 and the calculated atom ratio of P to Cu+Zr wasabout 1:1. The recovered, dried gel was divided into 2 portions. Portion1, solid 36S, was calcined for 4 hours in air at 500° C. Portion 2,solid 37S, was calcined for 4 hours in air at 300° C.

Gel B was prepared from 0.200 of Cu(NO₃)₂.2 1/2H₂ O, 0.400 mole ofZrOCl₂.4H₂ O and 0.600 mole of (NH₄)₂ HP)₄. The calculated atom ratioswere: Cu to Zr of about 0.5:1 and P to Cu+Zr of about 1:1. Therecovered, dried gel was also divided into 2 portions. Portion 1, solid38S, was calcined for 4 hours in air at 500° C. Portion 2, solid 39S,was calcined for 4 hours in air at 300° C.

The pore volume of solid 38S was determined to be 1.05 cc/g and thesurface area was 73 mL² /g; it is believed solids 36S, 37S, and 39S hadabout the same pore volume and surface area as 38S.

The atom ratios of Cu and Zr used, weights of precursor A and catalyststhereof are given in Table VII.

                  TABLE VIIA                                                      ______________________________________                                        Catalyst Precursors and Catalysts                                             ZrPO.sub.4 -Containing Solid   Isolated                                       Cat.        Atom Ratio                                                                              Calcining                                                                             Precursor A                                                                            Catalyst.sup.(a)                       No.  No.    Cu/Zr     Temp. °C.                                                                      Wt. g    Wt. g                                  ______________________________________                                        36   36S    0.7:1     500     21.3     4.8                                    37   37S    0.7:1     300     25.3     5.3                                    38   38S    0.5:1     500     25.9     5.0                                    39   39S    0.5:1     300     23.4     5.1                                    ______________________________________                                         .sup.(a) From 5 g portion of corresponding precursor A.                  

A weighed portion of each catalyst was employed in propylenepolymerization as described in Example V. The results obtained arereported in Table VIIB.

                  TABLE VIIB                                                      ______________________________________                                        Propylene Polymerization                                                                                          Melt                                           Weight,  Calculated            Flow  Flex.                               Cat. mg       Prod.,    Wt. % Solubles                                                                            g/10  Mod.                                No.  Cat.     kg/g/hr.sup.(a)                                                                         Propylene                                                                             Xylene                                                                              min.  MPa                               ______________________________________                                        36   206.8    0.427     2.7     4.1   42    1557                              37   129.4    0.988     2.5     6.3   27    1432                              38   105.4    1.19      1.8     3.8   56    1365                              39   153.9    0.276     5.3     4.5   77    1310                              ______________________________________                                    

The data reported in Table VIIB demonstrate that Cu/Zr/PO₂ xerogels canbe successfully employed in the preparation of the catalyst of thisinvention. The results suggest that a solid having a Cu/Zr atom ratio ofabout 0.7:1 (catalyst 36) results in a catalyst having a greateractivity than when a solid having a Cu/Zr ratio of about 0.5:1 (catalyst38) is used. The results also suggest, in comparing productivity valuesof catalyst 36 with catalyst 37 and productivity values of catalyst 38with catalyst 39, that the solids calcined at 500° C. give more activecatalysts than those calcined at 300° C.

The various catalysts are also responsive to hydrogen based on meltflows ranging from 27 to 77 g/10 min.

EXAMPLE IX

A catalyst (catalyst 40) was prepared in a manner similar to thepreparation of catalyst 23 except that the Ni/ZrPO₄ gel was prepared inthe presence of sulfate ions.

An 87 g (0.3 moles) sample of nickel nitrate hexahydrate, Ni(NO₃)₂.6H₂O, from Mallinkrodt and a 75.2 g (0.3 moles) sample of ZrOCl₂.4H₂ O fromAlpha were dissolved in 700 ccs of hot water while stirring, to form asolution.

Then 80.04 g (0.6 moles) of (NH₄)₂ HPO₄ and 39.6 g (0.3 moles) of (NH₄)₂SO₄, both obtained from Fischer, were dissolved in 300 ccs warm waterwith stirring to form another solution.

The two solutions were then mixed with stirring at approximately 69° C.for 30 minutes. A green gel was formed. The mixture was filtered and thesolid gel was washed with 500 mL of distilled water, then wastransferred to a beaker containing 750 mL of distilled water. Thecontents of the beaker were stirred while heating to 65° C. for 11/2hours. The contents were then removed and filtered to recover the gel,which was dried in a 120° C. vacuum oven overnight.

The dried gel was then removed from the oven and calcined at 450° C. for4 hours, followed by grinding to obtain a powder. The yield of powderwas 80.3 g.

A 20 g sample of the above-prepared ZrPO₄ material was employed in thepreparation of catalyst 40 as described in Example V. A comparison ofthe Ni/Zr atom ratio of the solid, the weights of precursor andcatalysts prepared therefrom are presented in Table VIIIA for catalysts23 and 40. Catalyst 23 was prepared identically to catalyst 40 exceptthat the ZrPO₄ solid used in the preparation of catalyst 40 was preparedin the presence of SO₄ ²⁻ ions.

                  TABLE VIIIA                                                     ______________________________________                                        Catalyst Precursors and Catalysts                                                    ZrPO.sub.4 -                                                                  Containing Solid                                                                       Atom                Isolated                                  Catalyst        Ratio      Precursor A                                                                            Catalyst.sup.(a)                          No.      No.    Ni/Zr      Wt. g    Wt. g                                     ______________________________________                                        23       21S    4:1        23.2     4.97                                      40       38S    4:1        25.7     4.6                                       ______________________________________                                         .sup.(a) From 5 g portion of corresponding precursor A.                  

A weighed portion of catalyst 40 was employed in propylenepolymerization as described in Example V. The results obtained are givenin Table VIIIB along with the results shown for catalyst 23 when it wasemployed in an essentially identical polymerization.

                  TABLE VIIIB                                                     ______________________________________                                        Propylene Polymerization                                                           Weight,  Calculated                                                      Cat. mg       Prod.,    Wt. % Solubles                                                                            Melt Flow                                 No.  Cat.     kg/g/hr.sup.(a)                                                                         Propylene                                                                             Xylene                                                                              g/10 min.                               ______________________________________                                        23   118.8    1.46      0.6     3.6   33                                      40    35.9    3.74      1.6     4.5   43.6                                    ______________________________________                                         .sup.(a) Based on polymer recovered from reactor excluding                    propylenesoluble polymer.                                                

Table VIIIB demonstrates that the presence of SO₄ ²⁻ ions during theZrPO₄ solid preparation results in a catalyst with higher productivitythan one that is prepared without the SO₄ ²⁻ ions. It is noted that useof the SO₄ ²⁻ containing solid produced slightly more soluble polymer;however, the SO₄ ²⁻ containing solid was observed to produce polymercrystal-like particles which grew large but had poor crush strength andthus fell apart upon handling the polymer.

While this invention has been described in detail for the purpose ofillustration, it is not meant to be limited thereby, but is intended tocover all reasonable modifications within the spirit and scope of theinvention.

That which is claimed is:
 1. A process for the polymerization ofalpha-olefins containing from 2 to 20 carbon atoms which comprisescontacting at least one of said alpha-olefins under polymerizationconditions with a catalyst prepared by(a) contacting at least one metaldihalide selected from the group consisting of Group IIA and IIBdihalides, with at least one transition metal compound consisting ofGroup IVB metal compounds in the presence of a diluent under conditionssuitable for the formation of a soluble complex; (b) contacting thesoluble complex produced in accordance with step (a) with about 1 toabout 99 wt. percent based on said soluble complex of a particulatematerial comprising zirconium phosphate to produce a first mixture; (c)contacting said first mixture with an organoaluminum halide to produce asolid catalyst precursor; (d) contacting said catalyst precursor withhalogen-containing compound selected from the group consisting of: TiX₄,SiX₄, SiHX₃, and mixtures thereof wherein X is a halogen atom.
 2. Aprocess in accordance with claim 1 wherein said transition metalcompound is a titanium tetrahydrocarbyloxide of the formula Ti(OR)₄,wherein each R is independently selected from the group consisting ofcarbon radicals having 1 to 20 carbon atoms.
 3. A process in accordancewith claim 1 wherein said particulate material further comprises othertransition metal ions selected from Groups IVB-VIB, IB, and IIB of thePeriodic Table.
 4. A process in accordance with claim 1 wherein saidparticulate material is prepared in the presence of sulfate ions.
 5. Aprocess in accordance with claim 1 wherein said olefin polymerizationcatalyst is employed with a cocatalyst comprising at least oneorganoaluminum compound, wherein the molar ratio of said cocatalyst totransition metal compound of said catalyst is in the range of 1:1 to1500:1.
 6. A process in accordance with claim 5 wherein said cocatalystfurther comprises a Lewis Base selected from the group consisting ofaromatic esters and amines, wherein the molar ratio of said Lewis Baseto said organoaluminum in said cocatalyst is in the range of 0.1:1 to0.6:1.
 7. A process in accordance with claim 6 wherein said Lewis Baseis selected from the group consisting of:ethyl benzoate, ethyl anisate,and 2,2,6,6-tetramethylpiperidine.
 8. A process in accordance with claim1 wherein hydrogen is present during the polymerization.
 9. A process inaccordance with claim 8 wherein said hydrogen is present in an amount inthe range of 20-40 psi.